Mechanical switch interlock

ABSTRACT

An interlock structure prevents inadvertent actuation of the second of a pair of relay switches after actuation of the first of the pair. Rods are moved into the nonactivated switch to block movement of its mechanism.

United States Patent [72] inventor [2 I] Appl. No. 22 Filed [45] Patented [73] Assignec [54] MECHANICAL SWITCH INTERLOCK 7 Claims, 4 Drawing Figs.

[50] Field of Search. 335/160, 161, 159; ZOO/50(3) [56] References Cited UNITED STATES PATENTS 3,240,889 3/1966 Lawrence 335/160 3,312,122 4/1967 Conner 335/160 Primary Examiner-Harold Broome Att0rney-Davis, Hoxie, Faithfull and l-lapgood ABSTRACT: An interlock structure prevents inadvertent ac- [52] U.S. Cl 335/160, tuation of the second of a pair of relay switches after actuation 200/50 of the first of the pair. Rods are moved into the nonactivated [51 Int. Cl H0lh 9/20 switch to bloclc movement of its mechanism.

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MECHANICAL SWITCH INTERLOCK The present invention is concerned with prevention ofinadvertent actuation of plural magnetically operated switches or relays. Such magnetically operated relay switches are widely used to control electrical power as the result of remote control pushbutton actuation. A typical application is the up and down control for an electric hoist. Pushing separate up and down pushbuttons causes actuation of motor control relay switches remote from the buttons which switches accomplish motor reversal. It is apparent that simultaneous pushing of both the up and down buttons is an expectable operator mistake, the consequences of which must be minimized. In the typical hoist control situation, such simultaneous button pushing can cause the forward and reverse windings of the motor to be simultaneously connected to the power line thereby causing a short or motor failure.

The present invention is directed to a novel mechanical in terlock which allows the only one of a pair of pushbutton controlled magnetically actuated relay switches to function, the other being locked against actuation.

In the Drawings:

FIG. 1 is a plan view of the assembly of a pair of magncti cally actuated relay switches provided with the novel interlock structure, the right-hand relay switch being a sectional view taken along the line l1 of FIG. 2;

FIG. 2 is an elevational view of the pair of relay switches of FIG. 1, the right'hand relay switch being a sectional view taken along the line 2-2 of FIG. I, and a portion of the lefthand relay switch being broken away to show the interlock structure;

FIG. 3 is a view of the right-hand end of the left-hand relay switch assembly taken along line 3-3 of FIG. 2: and

FIG. 4 is a partial perspective view of the interlock structure.

The drawings illustrate the invention in the context of a hoist motor control switch in which a pair of magnetically actuated relay switches or relays I and 12 are mounted on a common baseplate 8. One of the relay switches and 12 is intended to control power to the clockwise windings of the motor and the other to control the counterclockwise windings. These motor windings are connected to one of a pair of terminal groups and 16, there being three terminals in each group for the three-phase motor control. The power is connected to the other terminal groups 14 and 16.

A control station located remote from this assembly would have up and down pushbutton switches or thelike which are connected to terminal groups I8 and wired so as to energize the respective solenoid coil when'one of the pushbutton switches is closed.

Energization of the solenoid coil 20 magnetically attracts an armature 22 downward against return springs 48. Contact carriers 24 are associated with the armature 22. Movable contact members 26 are carried by the carriers 24 such that downward movement of the armature 22 causes contacts 26 to contact the fixed contacts 28 and 30 associated with the terminal groups 14 and 16 to complete a circuit between terminal groups 14 and l6. Movable contacts 26 are associated with the contact carriers with springs 32 to accommodate minor misalignment and to provide adequate contact pressure.

Auxiliary switches 34 and 36 are associated with the primary relay switches such that they also are actuated by the movement of the armatures. The auxiliary switches are used to'perform other functions such as the control of indicator lights or warning devices. Auxiliary switches 34 and 36 contain return springs and can be substituted for return springs 48.

lock rod and channel assembly towards a neutral position in the center ofthe space between relay switches 10 and I2.

Armature 22 includes a central longitudinal bar 23 which extends beyond the ends of the armature 22. The ends of bar 23 are shaped to provide cam surfaces which contact the adjacent roller 44 of the interlock assembly. When the armature of one relay switch is attracted downwardly by virtue of energization of its solenoid coil 20, the cam surface associated therewith causes the interlock structure to slide in a direction away from that relay switch. The cam surface of bar 23 cooperates with roller 44 to translate the vertical movement of the armature into horizontal movement of interlock rods 40.

Armature 22 also includes a transverse member 25, both ends of which protrude into the holes 41 in the relay switch housing in which interlock rods 40 slide. When one relay switch armature is activated, transverse member 25 is free to move downwardly because the rods 40 in the switch have been retracted by the cam action of bar 23 and roller 44. A rounded button 27 and rounded ends on bars 40 provide low frictional resistance to relative movement of the transverse member 25 of the activated switch and the bars 40 and also provide an added horizontal force component to the proximal ends of the rods to insure retraction of the bars from the activated relay switch.

The distal rod ends within the nonactivated switch are urged under the transverse armature member 25 of that switch. FIG. 4 shows the relationship between the rod ends and the armature transverse member 25 in the activated relay switch. The partial detail view included in FIG. 4 shows the rod end after it has moved under the transverse armature member of the nonactivated relay switch. When the rods 40 have been moved under the transverse armature members 25 of the nonactivated relay switch, the armature of that switch cannot move downwardly. The nonactivated relay switch is mechanically blocked and cannot move.

Movement of the nonactivated relay switch is further prevented by the presence under the cam surface on the longitudinal bar 23 of that switch of the adjacent roller 44. As can best be seen in FIG. 2, the roller 44 adjacent the nonactivated relay switch is urged under the protruding end of the cam surface. Downward movement of the nonactivated armature is arrested by interference between its cam surface and the roller.

The following is a summary of the operation of the assembly. A remote control switch, such as a pushbutton, is closed to supply current to the coil of the relay switch 10 or 12 associated with that remote control switch. The energized coil magnetically attracts the armature 22 of activated relay switch downwardly. The cam surface of armature longitudinal member 23 engages the roller 44 adjacent to the activated relay switch resulting in a horizontal movement of that roller ina direction away from the activated relay switch. Roller 44 is associated with channel member 42 of the interlock structure and channel member 42 is fixed to rods 40 through clips 43 thereby transmitting the horizontal motion of the roller to the rods 40 to retract the rods 40 from the activated relay switch. The armature 22 of the activated relay switch is free to complete its downward movement to establish electrical connection between fixed contact groups 30 and fixed contact groups 28 through contacting movable contacts 26. The circuit to the appropriate motor winding is completed. Horizontal movementof the interlock structure inserts the other ends of the rod into the nonactivated relay switch such that they pass under transverse member 25 of the nonactivated relay switch'thereby preventing downward movement of the nonactivated armature. Simultaneously, the roller 44 adjacent to the nonactivated relay switch is moved to a position directly under the cam surface of longitudinal bar 23 of the nonactivated relay switch to further prevent actuation of that switch.

Thus, the relay switch associated with the remote control switch first closed is allowed to be activated but the switch associated with another remote control switch is prevented from actuation.

Release of the remote control switch deenergizes the coil allowing the activated armature to return to the upward position by virtue of return springs 48 or the like. The biasing springs 46 retract the interlock structure from the nonactivated relay switch and cause the interlock to assume a neutral position in which either one of the switches can be selected for activation.

A further safety feature of this arrangement comes into force when the solenoid of the second of the relay switches is energized in error. The armature 22 of that second switch is prevented from effecting actuation by virtue of the interferencebetween the transverse member 25 and the interlock rods 40. However, magnetic attraction of the armature toward the erroneously energized solenoid will develop frictional force on rods 40 sufficient to overcome the neutral bias springs 46. Thus, the interlock rods are held in locking position in the second relay switch such that they will not retreat when the first relay switch is deenergized. The second switch must also be deenergized before the interlock rods can return to a neutral position. This feature prevents sudden and unexpected direction reversal when the first pressed remote control pushbutton is released.

Although the invention has been described in the context of solenoid actuated remotely controlled switches, it is apparent that the advantages of the interlock structure accrue to directly actuated switches whose movable contacts are actuated by manual pushbuttons, pneumatic or hydraulic actuators, or motion derived from machinery associated with the switches. It is further apparent that the invention is applicable to sets of plural switches and is not limited in application only to pairs of switches.

lclaim:

l. A mechanical interlock which permits actuation of only one of either of a pair of switches, said switches each including a movable member associated with the movable contacts of the switch, the movable members each having a cam surface extending longitudinally of the movable members to the exterior of the switches intermediate the pair, at least one element longitudinally slidable with respect to the switches and located so as to interfere with movement of the movable member when the element is advanced toward one of the switches to thereby block actuating motion of that movable member, said element having affixed thereto a cam surface follower such that actuating motion of one of the switches of the pair will cause the cam surface of that switch to engage the cam surface follower and advance the element into interference with the movable member of the other switch.

2. In the combination of a pair of remotely actuated switches and a mechanical interlock which permits actuation of only one of either of the switches of the pair, said switches being spaced from each other, said switches each including an armature associated with the moving contacts of the switch and an actuation mechanism which moves the armature to actuate the switch when the actuation mechanism is energized, the improvement which comprises a cam surface affixed to each armature and extending into the space between the pair, a transverse member affixed to each armature, an axially slidable rod extending between the switches and located such that when axially advanced toward one of the switches of the pair said rod will interfere with the transverse member of that switch to prevent actuating movement of that armature, and a cam surface follower associated with said rod such that actuation of one switch will cause its cam surface to drive said cam surface follower and associated rod toward the other switch to cause the rod to interfere with the transverse armature member of said other switch.

3. The combination of claim 2 wherein there are a pair of axially slidable rods which act in concert.

4. The combination of claim 3 wherein the cam surface follower is attached to both rods of the pair and is provided with rollers for contact with the cam surfaces of the switch armatures.

5. The combination of claim 2 wherein the length of the slidable rod is less then the distance between the transverse members of the pair of armatures.

6. A mechanical interlock which permits actuation of only one of either of a pair of solenoid actuated switches, said switches each including a movable armature associated with the movable contacts of the switch, a member centrally affixed to and transverse of the armature, at least one rod axially slidable with respect to the switches and located so as to interfere with the transverse member to prevent movement of one of the armatures when the rod is advanced toward that one of the switches to thereby block actuating motion of that armature, said rod being associated with the armatures such that actuating motion of the armature of one of the switches of the pair will axially advance the rod into interference with the transverse member of the other switch.

7. A mechanical interlock mechanism for a set of at least two switches which mechanism prevents actuation of one of said switches after actuation of another of said switches, said switches each including a movable member associated with the movable contacts of the switch, the movable members each having a cam surface extending longitudinally of the movable members to the exterior of the switches intermediate the switches, at least one element longitudinally slidable with respect to the switches and located so as to interfere with movement of the movable member when the longitudinally slidable element is advanced away from the first actuated switch to thereby block actuating motion of the movable member of the switch whose actuation is thereby prevented, said longitudinally slidable element having affixed thereto a cam surface follower such that actuating motion of the first actuated switch of the set will cause the cam surface of that switch to engage the cam surface follower and advance the longitudinally slidable element into interference with the movable member of the switch whose actuation is to be prevented. 

1. A mechanical interlock which permits actuation of only one of either of a pair of switches, said switches each including a movable member associated with the movable contacts of the switch, the movable members each having a cam surface extending longitudinally of the movable members to the exterior of the switches intermediate the pair, at least one element longitudinally slidable with respect to the switches and located so as to interfere with movement of the movable member when the element is advanced toward one of the switches to thereby block actuating motion of that movable member, said element having affixed thereto a cam surface follower such that actuating motion of one of the switches of the pair will cause the cam surface of that switch to engage the cam surface follower and advance the element into interference with the movable member of the other switch.
 2. In the combination of a pair of remotely actuated switches and a mechanical interlock which permits actuation of only one of either of the switches of the pair, said switches being spaced from each other, said switches each including an armature associated with the moving contacts of the switch and an actuation mechanism which moves the armature to actuate the switch when the actuation mechanism is energized, the improvement which comprises a cam surface affixed to each armature and extending into the space between the pair, a transverse member affixed to each armature, an axially slidable rod extending between the switches and located such that when axially advanced toward one of the switches of the pair said rod will interfere with the transverse member of that switch to prevent actuating movement of that armature, and a cam surface follower associated with said rod such that actuation of one switch will cause its cam surface to drive said cam surface follower and associated rod toward the other switch to cause the rod to interfere with the transverse armature member of said other switch.
 3. The combination of claim 2 wherein there are a pair of axially slidable rods which act in concert.
 4. The combination of claim 3 wherein the cam surface follower is attached to both rods of the pair and is provided with rollers for contact with the cam surfaces of the switch armatures.
 5. The combination of claim 2 wherein the length of the slidable rod is less then the distance between the transverse members of the pair of armatures.
 6. A mechanical interlock which permits actuation of only one of either of a pair of solenoid actuated switches, said switches each including a movable armature associated with the movable contacts of the switch, a member centrally affixed to and transverse of the armature, at least one rod axially slidable with respect to the switches and located so as to interfere with the transverse member to prevent movement of one of the armatures when the rod is advanced toward that one of the switches to thereby block actuating motion of that armature, said rod being associated with the armatures such that actuating motion of the armature of one of the switches of the pair will axially advance the rod into interference with the transverse member of the other switch.
 7. A mechanical interlock mechanism for a set of at least two switches which mechanism prevents actuation of one of said switches after actuation of another of said switches, said switches each including a movable member associated with the movable contacts of the switch, the movable members each having a cam surface extending longitudinally of the movable members to the exterior of the switches intermediate the switches, at least one element longitudinally slidable with respect to the switches and located so as to interfere with movement of the movable member when the longitudinally slidable element is advanced away from the first actuated switch to thereby block actuating motion of the movable member of the switch whose actuation is thereby prevented, said longitudinally slidable element having affixed thereto a cam surface follower such that actuating motion of the first actuated switch of the set will cause the cam surface of that switch to engage the cam surface follower and advance the longitudinally slidable element into interference with the movable member of the switch whose actuation is to be prevented. 